Microphone with carbon-powder fall for strong currents.



G. B. MARZI. MICROPHONE WITH CARBON POWDER FALL FOR STRONG CURRENTS.

APPUCATION FILED FEB. l2, I914.

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WITNESSES W 46 r ram/E rs G. B. MAHZI. MICROPHONE WITH CARBON POWDER FALL FOR STRONG CUHRENTS. APPLICATION FILED FEB-2.19M.

1 ,237, 933. Patented Aug. 21, 1917.

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Be 'it known that I,"1GIOVAN BLATIISTA" Maazrg electrician, a subjebt'of'the-K'ingiof Italy, =resi'dingT5at' Cornigliano' Ligure in the' Province 'ofiorenca and Kin dom-i *Ita'ly, have inventedflce'rta'innew and useful In'r provemenfis i115:Microphoneswith 7 Garborr' Powder Fall for Strong (lurrentsyof which the remain em specification, reference bein'gLhad therein'to the 'accompanyingalraiw irigs 1 All electrical microphones including Icarbon underway formg'sueh as powder,- pieces, giains,' rtfds;='=dieks;=have thegreat 'disad-vamtage that the carbon owing to"the"continhal passage of excessively strong-electric curreht gets l heated uritil itbeccmee incandescent," and 'in' this] attersta te 'its surface gets coated with an-"insitlating' crust of as p'which inmeasesgraduahy the innerresistan'ce of the micreplmnww such an extent "astou'ender it inactive- Scverarkinus cfearbcwmicroplmnshav been experimented'with in trying-to elimi nate' br an least to diminish this defect but" up todate these efior'ts have led tono'fav'or able' result, nor' has' anyhotemorthyz: ad vantage beemsec'ured with artificiahcoolihg 1 produced "by the) 'circulat'i'on 'of water or of air. Such inadequate "means have repeat edly; been tried toi eliminating the above de feet, but without an y' r eal result.

A measure preventing the evil attherobt consists, on the coatrarwin eliminating the causes, instead o the"eflects,'-of' the defect. This is obtained according to the present invent'itir'i} by renewingcontinuallytheearbdw Fig. 2 is a partiall'modification of Figsl; -Fig 3 isam'odification"oi the swinging valve;

nectlons.

The fundamental idea of this invention rrray be hpp'lied'to anytelephonic apparatus; here-is-shown,'by way of examp'leflts application'zto 7a telephonic transn1itter,'in which is-em'gloye'dialever with two arms 23-, of which the-arm swln'gsbetween the peles of an eliitromagnet 1', while the arm*-':-3-'' controlsi'as explained hereinafter, the brifice at a carbon powder chute l.

A reservoir -5 contains'a certain'quair- 'ofi fine-grained carbon powder; its lower portion is funnel shaped and carries a 'tubul'arrexfiension 5-4:- open at its lower en'dll The outlet of the carbon-powder is controlledby ach'eck-valve T- having a spherica'l fl ig. -1), or" conical shapc 'S- (Fig: *3) 91;" any other convenient shape whatever. endof'the"arm 3 oscillating between the poles of :the electromagnct 1. eontrivanm is regulated in such manner that in"the.positi'on of rest, the valve closes the lower orifice of. the tube l. preventing 'thus the'ffailing'down of tlrefcarlmn powder, while when in operation, the vibrationsof the le vers 'Z-andfl opeln'and close alternately the said'orifiee', so that'atevery. opening of'the latter a cezrtainquantityot"tire carbon powder-falls-glQWm'caUsing-thus a continuous change-of the; lower layers of the carbon powder which are just those through which passes" tlreeleetric'-'-current.' The continuous which forms the contacts of variable iesit- "ren'w'2[1 of these layers of carbon powder ance so that it cannot become heated.

The heating and the subsequent incandescence of a carbon mass take place only gradually within a determined period of time. It is, therefore, important not to leave a given carbon mass under the influence of the passage of the electric current bevond a certain space of time, that is to say for a time suflicient to heat the mass excessively; or, in other words, as already stated, it is imperative to renew the carbon, thus providing a kind of circulation of powder in the same way as the circulations of liquids or of gas are established.

In the annexed drawing, which shows a practical embodiment of the invention,

Figure 1 is a side elevation of the carbon feeding apparatus;

prevents them from becoming excessively heated, as would be the case if they were not continuously renewed. At the same time the vibrations of the lever modify the pressure of the carbon-powder column, thus permitting the s eech to be transmitted. The surfaces of t e electrodes, which are in contact with the carbon mass and influenced by the passage of the current, are covered with a platinum plate 9.

The carbon-powder which falls down is collected in a vessel 10 placed beneath, from which it is poured periodically in the reservoir -5-.

Another embodiment is illustrated in Fig. '2. A glass funnel -11 has its lower end cut obliquely at about 45; inside it is covered with a metallic plate 12 which is Fig. 4 1's a 'di'zigramof the electrical coir The said valve is fastened at the slightly shorter than the glass tube; at the upper end of this plate projecting from the funnel is provided a binding-screw -13-, where ends one of the wires of the circuit; the chec| -valve or check-door is formed by a plate --l4- linked with a pivot 1.5 at the end 3 of the lever of the electromagnot, and forming an inclined plane, which facilitates the gliding down of the carbonpowder. In this embodiment the lever swings in the horizontal plane, while in the embodiment described above it must swing in the vertical plane. From the lever -23- starts the other wire of the micro phonic circuit.

Fig. 4 shows the way in which this mirrophone in practice is inserted in a circuit, for instance for radiotelephonic transmissions. In said Fig. 16- is a microphone of the ordinary type as used for the usual telephonic transmissions; 17 is the battery which feeds the microphonic circuit 1S comprising a circuit-breaker --l9- and the primary winding 20 of the transformer coil. The secondary winding -21- of this transformer belongs to a circnit -22 comprising the eleetromagnet 1- which acts on the lever 2-3. This leverxopeiates the microphone with carbonpowder fall according to the present invention, which in the diagram is supposed to be formed by two carbon rods 23-24 cut obliquely, of which that movable horizontally -2i is a solid rod, while the vertical rod 23 is hollow and serves as outlet for the vessel with the powder. At the two carbon rods 23-24 are fastened the ends -Q526 of the oscillating transmitting circuit.

Having now fully described this my invention, and how the same is to be carried out, I declare that what I claim is:

1. In a microphone employin a powdered carbon contact, a carbon supp and electrically actuated means for controlling the delivery of the carbon from the supply to renew the carbon contact.

2. In a microphone employing a powdered carbon contact, a carbon supply, a valve in circuit with the said contact and commanding the said supply, and electrically controlled means responsive to variations in the electric current of the circuit for actuating the valve to vary the pressure on the contact and to renew the same from the said supply.

3. In a microphone, a supply of granulated carbon, a chute through which said carbon is allowed to fall, movable parts controlling the fall of the carbon, and an electric circuit in which the falling carbon forms a contact medium.

4. The combination of a microphone employing a powdered carbon contact, a supply of granulated carbon, movable parts controlling the fall of the carbon, and a second microphone actuating the movable parts which act on the falling carbon constituting the contact medium.

5. The combination of a primary microphone, an electromagnet inductively energized by the variation of current in said primary microphone, a vibrating lever, one arm of which swings between the poles of said electromagnet, a valve at the end of the other arm of said lever, a supply of carbon, a receptacle therefor, the said valve controlling the fall of the carbon contained in the receptacle, the falling carbon constituting the contact medium of a microphone for strong currents flowing through a circuit including the valve and the receptacle.

In testimony whereof I atlix my signature in presence of two witnesses.

LE'ITERIS LABOGCETTA, ANTONINO LABOCCETTA.

Copies of this patent may be obtained for five cents each, by addressing the "Commissioner of Patents.

Washington, I). C." 

